<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019faa90-4f00-78c7-a6e7-4164198cd81f,g:5c21b517-2648-4626-898c-f3dfcbdd6501-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.mainstcapital.com/role/Cover" xlink:type="simple" xlink:href="msif-20260806.xsd#Cover"/>
  <link:presentationLink xlink:role="http://www.mainstcapital.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CoverAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019faa90-4f00-7449-b9c4-95b7b4b523d3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_DocumentType_019faa90-4f00-7449-b9c4-95b7b4b523d3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019faa90-4f00-765b-98f8-cee869366b36" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_DocumentPeriodEndDate_019faa90-4f00-765b-98f8-cee869366b36" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019faa90-4f00-75ba-aad3-d3de70d67d4a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityRegistrantName_019faa90-4f00-75ba-aad3-d3de70d67d4a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019faa90-4f00-7747-a7d4-182356112fe0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019faa90-4f00-7747-a7d4-182356112fe0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019faa90-4f00-7ea2-9cab-417c51ed5328" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityFileNumber_019faa90-4f00-7ea2-9cab-417c51ed5328" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019faa90-4f00-78f1-911c-b390156d62da" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityTaxIdentificationNumber_019faa90-4f00-78f1-911c-b390156d62da" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019faa90-4f00-7e1e-a558-8c87b1a5f3ab" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityAddressAddressLine1_019faa90-4f00-7e1e-a558-8c87b1a5f3ab" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019faa90-4f00-7bbb-a61a-98989840d3b3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine2"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityAddressAddressLine2_019faa90-4f00-7bbb-a61a-98989840d3b3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019faa90-4f00-7eeb-8995-0755556a9ab2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityAddressCityOrTown_019faa90-4f00-7eeb-8995-0755556a9ab2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019faa90-4f00-76b4-85e9-91a6e2951be5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityAddressStateOrProvince_019faa90-4f00-76b4-85e9-91a6e2951be5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019faa90-4f00-7c37-826a-d156b7a9be44" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityAddressPostalZipCode_019faa90-4f00-7c37-826a-d156b7a9be44" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019faa90-4f00-7c73-aef5-0ab5a4afe455" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_CityAreaCode_019faa90-4f00-7c73-aef5-0ab5a4afe455" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019faa90-4f00-7c47-8086-a7a8cce94a47" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:presentationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_LocalPhoneNumber_019faa90-4f00-7c47-8086-a7a8cce94a47" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019faa90-4f00-7277-90e4-37a76eee4db5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_WrittenCommunications"/>
    <link:presentationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_WrittenCommunications_019faa90-4f00-7277-90e4-37a76eee4db5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019faa90-4f00-7587-a683-08a19b03c52e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SolicitingMaterial"/>
    <link:presentationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_SolicitingMaterial_019faa90-4f00-7587-a683-08a19b03c52e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019faa90-4f00-730a-a940-aab9c7bfc0b1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_PreCommencementTenderOffer"/>
    <link:presentationArc order="16" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_PreCommencementTenderOffer_019faa90-4f00-730a-a940-aab9c7bfc0b1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019faa90-4f00-7454-b9e5-d593d2e21491" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:presentationArc order="17" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019faa90-4f00-7454-b9e5-d593d2e21491" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019faa90-4f00-7c85-8e51-281bb1a66e9a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:presentationArc order="18" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityEmergingGrowthCompany_019faa90-4f00-7c85-8e51-281bb1a66e9a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019faa90-4f00-7344-9cd4-f6b9d415aac9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:presentationArc order="19" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityCentralIndexKey_019faa90-4f00-7344-9cd4-f6b9d415aac9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019faa90-4f00-7cd7-bbc2-b5eff2a1dd9a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:presentationArc order="20" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_AmendmentFlag_019faa90-4f00-7cd7-bbc2-b5eff2a1dd9a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsTable_019faa90-4f00-7ce9-bc66-03cc5143c284" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityListingsTable"/>
    <link:presentationArc order="21" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019faa90-4f00-7990-9914-6c0837b82f73" xlink:to="loc_dei_EntityListingsTable_019faa90-4f00-7ce9-bc66-03cc5143c284" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsLineItems_019faa90-4f00-7f3f-9f15-717aad0f165f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityListingsLineItems"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsTable_019faa90-4f00-7ce9-bc66-03cc5143c284" xlink:to="loc_dei_EntityListingsLineItems_019faa90-4f00-7f3f-9f15-717aad0f165f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019faa90-4f00-7bec-9100-6b396c93b2ad" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsLineItems_019faa90-4f00-7f3f-9f15-717aad0f165f" xlink:to="loc_dei_SecurityExchangeName_019faa90-4f00-7bec-9100-6b396c93b2ad" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019faa90-4f00-7da0-b046-ed95b77654f3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsLineItems_019faa90-4f00-7f3f-9f15-717aad0f165f" xlink:to="loc_dei_TradingSymbol_019faa90-4f00-7da0-b046-ed95b77654f3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019faa90-4f00-7579-bbb4-1c498ba8b01e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsLineItems_019faa90-4f00-7f3f-9f15-717aad0f165f" xlink:to="loc_dei_Security12bTitle_019faa90-4f00-7579-bbb4-1c498ba8b01e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
</link:linkbase>
